This invention relates to a process for continuously making a disposable pants-type diaper.
Japanese Patent Application No. 1991-139349A discloses a process for continuously making a disposable pants-type diaper having a pair of elastically stretchable leg-holes. This process of well known art comprises the steps of: continuously feeding two elastic members spaced from each other in the direction orthogonal to the machine direction and securing them to one surface of a web continuously fed into the machine direction so that these two elastic members are opposed to each other with a region destined to define respective leg-openings therebetween; and cutting the web in conformity with the expected configuration of the leg-openings to form the leg-openings provided along peripheral edge regions thereof with the elastic members.
Japanese Patent Application No. 1997-224973A also discloses a process for continuously making a disposable diaper having a pair of elastically stretchable leg-holes. This process of well known art comprises the steps of: continuously feeding a web in a machine direction and securing two strips of continuous running elastic members in the machine direction so as to describe substantially sinusoidal curve of to one surface of the web; cutting the web along the curve of the strips delineated by these elastic members between these two streaks of the elastic members into upper and lower parts; separating these two portions of the web hereafter called web halves to the direction orthogonal to the machine direction by a desired dimension and then shifting one of the web halves separated to the machine direction by the distance corresponding to half a cycle of the substantially sinusoidal curve; and bonding these web halves in such regions as overlapping each other. In the web halves bonded in this manner, edges extending in the machine direction so as to describe substantially sinusoidal curves in which each pair of crest and trough opposed to each other define leg-opening. The leg-opening is provided along its peripheral edge region with the elastic members.
The process for making a diaper disclosed in the Japanese Patent Application No. 1991-139349A is adapted to form the leg-openings of the diaper by cutting out parts of the web. Consequently, pieces of waste material each having a shape in conformity with each leg-opening are inevitably generated, so labor and cost are required for disposal of these pieces of the waste material.
With the process for making the diaper disclosed in the Japanese Patent Application A No. 1997-224973, the web halves running in parallel to each other must be shifted twice, i.e., in the machine direction and in the direction orthogonal to the machine direction. Control of the process is correspondingly complicated and it becomes difficult to improve the productivity.
It is an object of this invention to provide a process for making a pants-type diaper having elastically stretchable leg-openings improved so that generation of waste material from web can be minimized and a frequency of shifting the running web can be also minimized.
According to this invention, there is provided a process for continuously making a pants-type diaper having a body fluid absorbent pad member curved in a U-shape along a crotch region and extending into front and rear waist regions, a sheet-like front waist member attached to an outer surface of the pad member in the front waist region so as to cover a half of the waist region in circumferential direction hereafter called waist half and a sheet-like rear waist member attached to the outer surface of the pad member in the rear waist region so as to cover another waist half in the circumferential direction wherein respective transversely opposite side edge regions of the front and rear waist members are joined together to form a circular waist region and cooperate with the pad member to define a pants-shape.
The process further comprises the steps of:
a. continuously feeding a single web destined to form the front and rear waist members in a machine direction and, at the same time, continuously feeding under extension a first elastic member extending in a machine direction so as to describe half a cycle of a substantially sinusoidal curve within a length corresponding to each of the waist halves being consecutive in the machine direction and securing this first elastic member to one surface of the web using an adhesive while a second elastic member being symmetric to the first elastic member about a center line bisecting a width of the web in a direction orthogonal to the machine direction is continuously fed so as to describe a curve phase-shifted with respect to the first elastic member by a half cycle and to be adjacent to the first elastic member in the orthogonal direction and secured to the one surface of the web using the appropriate adhesive, and thereby forming a composite web;
b. cutting the first composite web between the first and second elastic members so as to bisect this composite web in the orthogonal direction and separating them from each other by a predetermined dimension in the orthogonal direction to form first and second web halves running in parallel to each other in the machine direction;
c. placing, substantially in a middle of the length corresponding to the half cycle of the front waist region in the machine direction, a body fluid absorbent solid pad member extending in the orthogonal direction and having a dimension in the machine direction being shorter than the length of the half cycle upon each pair of the first web half and second web half to bridge and joining them to these web halves to form a first series of diapers running in the machine direction;
d. folding back, in the orthogonal direction, the first series of diapers along a center line dividing the first series of diapers into upper and lower parts with the pad member inside so as to form a second series of diapers;
e. joining each pair of the first and second web halves placed upon each other in the second series of diapers together substantially in the middle of each pair of the adjacent pad members to form joining regions arranged intermittently in the orthogonal direction between each pair of the adjacent pad members; and
f. cutting the second series of diapers along a cutting line extending in the orthogonal direction through one of the joining regions and in a vicinity of the joining regions to obtain an individual diaper having the first and second web halves joined together along both side edges of the pad member.
The process according to this invention for continuously making the disposable diaper enables the front and rear waist members to be obtained merely by transversely bisecting, along the substantially sinusoidal curve, the web continuously fed in the machine direction and then moving the respective web halves away from each other in the direction of cd. Accordingly, no waste material is generated and such troublesome work as the treatment of waste material is not required. Furthermore, the process is simplified in comparison to the conventional process by the prior art and easily controlled. As a result, productivity of the diaper is correspondingly enhanced.